Railroad car draft gears have been used for many years at opposite ends of a railcar to absorb and cushion impact forces. Most railcar draft gears include a cast housing having an inwardly tapered bore at an open end, a spring disposed within the housing, a series of metal friction shoes or members arranged in the tapered bore of the housing and movable against the spring upon compression of the draft gear, and a wedge disposed in operable combination with the friction members such that impact blows directed against the wedge are transferred axially to the spring and radially to the housing. In most railcar draft gears, a spring seat or follower is arranged between an end portion of each friction member and the spring.
Recently, elastomeric materials have been used and accepted as replacements for steel springs. While offering advantageous results, unless the load applied to the elastomeric spring is perfectly aligned with the longitudinal axis of the spring, elongated elastomeric springs tend to snake or buckle under load. One elastomeric spring assembly offering beneficial results is disclosed in U.S. Pat. No. 5,351,844 to R. A. Carlstedt and includes multiple elastomeric springs stacked in axial relation relative to each other. A metal plate is bonded or otherwise secured to opposed faces of each elastomeric spring. The metal plate bonded to each face of each elastomeric spring offers numerous advantageous results. The metal plates act to limit snaking and/or buckling problems. Moreover, the metal plates bonded to opposed faces of each elastomeric spring yields increased work capacity from each spring. Such a spring assembly has been successfully used for years in combination with railcar draft gears.
Railcar manufacturers and suppliers for such railcar manufacturers are continually seeking methods and ways of reducing the manufacturing costs of railcars and the components used to build such railcars without having to sacrifice performance and quality. When considering costs savings in connection with draft gears, however, the options are few. First, the size of the draft gear housing cannot be changed without adversely effecting the relationship with a fixed size pocket provided in a railcar centersill in which the draft gear is accommodated. Second, and with the size of the draft gear housing being fixed, the amount of steel used to form the draft gear housing has already been minimized as with openings and voids wherever possible. Moreover, the size of the elastomeric spring assembly used in the draft gear to absorb impacts, as defined by the number of the elastomeric springs comprising the spring assembly, cannot be reduced without adversely effecting draft gear performance and operation.
Thus, there remains a continuing need and desire to provide a railcar draft gear capable of offering the same operating characteristics as known railcar draft gears but which is more economical to manufacture.